I have a small VPS service that I use primarily to run a tor bridge (and also a VPN).
Sometimes I travel to China for work, so I have the bridge configured as unlisted and only connect to it with obfs4 - and it manages to not get blocked by the Great Firewall. For convenience I have all my various devices configured to use the bridge, even when at home.
For $5 a month, I have 1,000 GB of monthly bandwidth with this server, but I never come close to using it all. There is an option (for an extra $2 per month) to add an extra IPv4 address. I am thinking of somehow configuring tor to use one IP address as the unlisted obfs4 bridge, and to run a middle relay on the other IP address.
Are there any potential problems with doing this? If not, then are there any instructions on how I might go about this? Do I need to run two tor instances, or can I somehow do it all with one?